Formatted question description: https://leetcode.ca/all/405.html

405. Convert a Number to Hexadecimal

Level

Easy

Description

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two s complement method is used.

Note:

  1. All letters in hexadecimal (a-f) must be in lowercase.
  2. The hexadecimal string must not contain extra leading 0s. If the number is zero, it is represented by a single zero character '0'; otherwise, the first character in the hexadecimal string will not be the zero character.
  3. The given number is guaranteed to fit within the range of a 32-bit signed integer.
  4. You must not use any method provided by the library which converts/formats the number to hex directly.

Example 1:

Input:
26

Output:
"1a"

Example 2:

Input:
-1

Output:
"ffffffff"

Solution

First convert num into 8 parts, each of which can be represented by a hexadecimal number with length 1. Convert each part to hexadecimal and concatenate the parts. Avoid leading zeroes.

class Solution {
    public String toHex(int num) {
        if (num == 0)
            return "0";
        int[] bytes = new int[8];
        for (int i = 0; i < 8; i++) {
            int temp = (num >> 4 * i) & 0xf;
            bytes[7 - i] = temp;
        }
        String hex = "";
        boolean flag = false;
        for (int i = 0; i < 8; i++) {
            int curByte = bytes[i];
            if (!flag && curByte == 0)
                continue;
            hex += hexChar(curByte);
            flag = true;
        }
        return hex;
    }

    public char hexChar(int num) {
        if (num < 10)
            return (char) (num + '0');
        else
            return (char) (num - 10 + 'a');
    }
}

All Problems

All Solutions